The formation of or accumulation of soils on hard surfaces or in a treatment zone is undesirable for both esthetic and operational reasons. Sulfur soils can be unsightly. Further, such soils can often reduce the efficiency of the chemical treatment for the overall treatment efficiency of a treatment zone. Treatments that can prevent the formation of or remove soils from a treatment zone can substantially improve operating efficiencies. Both organic and inorganic soils can accumulate in a variety of chemical treatment zones. Inorganic soils can be particularly troublesome. Such soils can include nonionized soils such as elemental sulfur, elemental carbon, etc. Such soils can also include anionic or cationic soils. Important soils include soils comprising carbonates (CO3−2), silicates (Na2O.xSiO2), sulfates (SO4−2), sulfites (SO3−2), sulfides (Sx−2,x=1–8), elemental sulfur, phosphates, (HPO4−2, PO4−3, etc.), or mixtures thereof.
In one embodiment of the use of such treatment zones, the treatment of a gas streams for the purpose of removing hydrogen sulfide and other mercaptan compounds is common. In natural gas processing, ethylene, propylene, flue gas, industrial gas is effluents and other commercial gas streams commonly containing hydrogen sulfide and mercaptan odor ingredients can be treated for contaminate removal. Further, industrial plants, agricultural installations, hospitals, kitchens, etc. that handle large quantities of organic material such as hog farms, dairy farms, chicken farms, meat packing plants, animal rendering plants, composting plants, paper mills, sewage treatment plants and other similar installations can generate large quantities of odors that typically exit the facility in an odor contaminated atmospheric effluent flume or other effluents. Such an effluent can contain a large variety of odoriferous or odor causing inorganic and organic chemicals or molecules including organic sulfides or organic thiols (mercaptans), monoamines, diamines, triamines, ammonia, alcohols, formaldehyde, acetaldehyde, carboxylic acids, skatole, carbon disulfide and hydrogen sulfide and other odor forming oxidizable compounds. An atmospheric effluent having one or more of such compounds can have a strong odor and can be highly objectionable within the plant to plant personnel and outside the plant to plant neighbors. In many gas treatment facilities, hydrogen sulfide and related mercaptan materials are contented with oxidizing agents that under common processing conditions result in the formation of elemental sulfur (S°). This sulfur can form a deposit, commonly in combination with other soils such as inorganic soils, organic soils, hardness components of service water, and other materials that can associate with the elemental sulfur in a soil deposit. Such soils can rapidly plugged in the gas transport tabs within the treatment structure. Such plugging reduces the volume of gas that can be treated, increases the pressure drop within the equipment and increases the cost of operating the gas transport device. The ability to inhabit sulfur deposit formation, or if deposits are present, to remove sulfur deposit is an important goal.
An odor is a gas phase emission that produces an olfactory stimulus. The odor thresholds of many chemicals that act as odor compositions common throughout the chemical process industries include, for example, ethyl sulfide having an odor threshold in the atmosphere of 0.25 parts per billion (ppb), hydrogen sulfide with an odor threshold of 0.4 ppb, dimethyl sulfide with an odor threshold of 1.0 ppb, ethyl mercaptan with an odor threshold of 1.0 ppb, methyl mercaptan with an odor threshold of 1.1 ppb. With a low threshold a small amount of these and similar odors common in plant effluent are serious olfactory problems. Such odors result from processing large quantities of organic materials and are generated by the action of micro-organisms in any biologically active system on a source of organic material producing the odors. There are many other sulfur odor producing chemicals possible, however, as shown in this representative, non-inclusive list:
1. Sulfur Compounds
Hydrogen Sulfide Thiophene
Carbonyl Sulfide Isobutyl Mercaptan
Methyl Mercaptan Diethyl Sulfide
Ethyl Mercaptan n-Butyl Mercaptan
Dimethyl Sulfide Dimethyl Disulfide
Carbon Disulfide 3-Methylthiophene
Isopropyl Mercaptan Tetrahydrothiophene
tert-Butyl Mercaptan 2,5-Dimethylthiophene
n-Propyl Mercaptan 2-Ethylthiophene
Ethyl Methyl Sulfide Diethyl Disulfide
Other sources of voter are present in many gas is effluents. These odor sources are not capable forming elemental sulfur deposits however they can no big a part of the deposit and can in certain circumstances in proved a the tendency of a sulfur to form deposits.
2. Organic Nitrogen Compounds
Primary amines
secondary amines
tertiary amines
pyridines
amides
ammonia
3. Organic Oxygen Compounds (Oxo-Hydrocarbon Compounds)
primary alcohols
carboxylic acids
aldehydes
ketone compounds
phenolics
Attempts have been made to reduce the production of the odor compounds and to reduce the release of the odor compounds from plants. Robinson, “Develop a Nose for Odor Control”, Chemical Engineering News, October 1993 contains a generic disclosure of odor problems and conventional odor control using aqueous treatment compositions including H2O2, FeCl3, KMnO4, NaOH and others. Careful control over the organic materials within the plant and reduction of microbial populations within the plant have been attempted to reduce the generation of the odor compounds in the plant atmosphere. Attempts to scrub the odor compounds from the plant atmosphere have been made using a variety of simple absorptive and oxidizing scrubbing materials. Fragrance chemicals that simply mask the offensive odors have been tried. In fact, essential oils have been used previously as odor masking compounds.
Sodium hydroxide (NaOH), activated carbon are useful absorptives. Oxidizing materials such as ozone (O3), chlorine dioxide (ClO2), sodium hypochlorite (NaClO) and others have been attempted. Some degree of success has been achieved using these oxidative materials to remove organic odor molecules from atmospheric effluents. While chlorine dioxide has had some success, chlorine dioxide is highly toxic, difficult to handle and must be generated on site. Such difficulties lead to substantial resistance to its use. Further, hydrogen peroxide is also known for odor control. Hydrogen peroxide by itself is not effective against a broad range of odor constituents without additional treatment materials. However, the application of oxidative technologies including ozone, hydrogen peroxide, chlorine dioxide and other oxidants have had some limited success.
The use of peroxyacid materials in microbiological methods are also known. For example, Grosse-Bowing et al., U.S. Pat. Nos. 4,051,058 and 4,051,059 disclose peroxyacetic containing antimicrobial compositions. Stas et al., U.S. Pat. Nos. 4,443,342 and 4,595,577 disclose the treatment of waste water and waste gases containing dialkyldisulfides by metal catalytic oxidation of these compounds by means of a peroxide compound in an aqueous medium. Lokkesmoe, U.S. Pat. No. 5,409,713 teaches peroxyacetic materials as microorganism sanitizers or growth inhibitors in aqueous transport systems typically containing produce and large amounts of challenged soil load.
Fraser, in “Peroxygens in environmental protection”, Effluent and Water Treatment Journal, June 1986 disclose that hydrogen peroxide (H2O2) can be used to reduce odor. Fraser only discusses microbial control with peroxyacetic acid and does not correlate odor control to peroxyacid treatment or concentration. Littlejohn et al., “Removal of NOx and SO2 from Flue Gas by Peroxyacid Solutions”, Ind. Eng. Chem. Res. Vol. 29, No. 7, pp. 1420–1424 (1990) disclose peroxyacids in removing nitric oxides and sulfur dioxide from coal fire derived flue gas.Lokkesmoe et al., U.S. Pat. No. 6,015,536, issued Jan. 18, 2000; Hei et al., U.S. Pat. No. 6,183,708, issued Feb. 6, 2001 and Hei et al., U.S. Pat. No. 6,277,344, issued Aug. 21, 2001 teach aspects of peracid odor reduction.
Peroxyacetic acid, neat and in aqueous solutions containing peroxyacetic acid has a strong pungent oxidizing odor resembling but stronger than acetic acid. Such materials have not been seriously considered as odor reducing materials because of the nature of its odor. The concern being that in any treatment process using a significant amount of peroxyacetic acid, the resulting treated effluent would inherently obtain the pungent odor of the peroxyacetic acid. Further, peroxyacetic acid solution inherently contain large amounts of acetic acid (HOAc).
Generally, the method of reducing odor involves using oxidizing agent to oxidizing the order component to a substantially reduced odor or odor free component. The oxidizing agent is presumed to act to oxidize many of the components of the gaseous stream. Hydrogen sulfide and many (—SH) sulfur compounds are oxidize to elemental sulfur using the following reaction sequence.2—SH+O2→2S°+H2OThe theoretical reaction sequence (due to the empty valence in the —SH group) demonstrates that hydrogen sulfur compounds can be oxidized to elemental sulfur. This inorganic sediment, often along with other inorganic sediments including carbonates, carbon soot, phosphates, sulfates, etc., can yield substantial scale deposits in odor control systems. Consequently, there remains a need for sulfur containing gas treatment processes that avoid formation of elemental sulfur, and other inorganic materials, in the oxidizing systems.